Electrosurgical apparatus having a safety circuit

• US 4,662,369 A
• Filed: 04/04/1986
• Issued: 05/05/1987
• Est. Priority Date: 04/04/1986
• Status: Expired due to Fees

• Current Assignee: MDT Incorporated, Santa Barbara Research Center Goleta CA
• Original Assignee: Castle, Inc.
• Inventors: Ensslin, Frieder H.
• Primary Examiner(s): Cohen, Lee S.
• Application Number:
  US06/848,076
• Time in Patent Office: 396 Days
• Field of Search: 128/303.13, 128/303.14, 128/303.17, 128/908
• US Class Current: 606/35
• CPC Class Codes: A61B 18/1233 with circuits for assuring patient safety
• CPC Class Codes: Y10S 128/908 Patient protection from electric shock

Abstract

An electrosurgical device having a generator for producing a radio frequency current. The device senses an RF current leakage and thereby reduces the output of the RF generator so as to limit the amount of RF leakage to levels below a predetermined value.

Claims

1. An electrosurgical device having a chassis ground, comprising a radio frequency generator having its output connected to an output transformer having an output lead and return lead;

a first leakage capacitance between said output lead and said chassis ground;

a second leakage capacitance between said return lead and said chassis ground;

means for sensing RF current leakage in said electrosurgical device comprising a sensing transformer having a primary side and secondary side, said primary side having a first and second leads, said first lead of said primary side of said sensing transformer being connected to said chassis ground, a first sensing capacitor being electrically connected between said output lead and second lead of said primary side of said sensing transformer, a second sensing capacitor electrically connected between said return lead and said second lead of said primary side of said sensing transformer, said secondary side of said sensing transformer producing a signal in response to said RF current leakage in said device, means for limiting the power output of said generator in response to said signal reducing said RF current leakage below a predetermined value.

2. An electrosurgical device according to claim 1 further characterized by said secondary side of said sensing transformer produces a signal in response to the following relationship:

space="preserve" listing-type="equation">CL1/CS1=CL2/CS2

wherein;

CL1=said first leakage capacitance

CL2=said second leakage capacitance

CS1=said first sensing capacitor

CS2=said second sensing capacitor.

3. An electrosurgical device according to claim 1 further characterized by said means for limiting the power output of said generator comprises an amplifier connected to a said secondary side of said sensing transformer, the output of said amplifier produces a negative feedback control signal in response to the RF current leakge for controlling the output of said generator.

4. An electrosurgical device having chassis ground comprising a radio frequency generator having its output connected to an output transformer having an output lead and a return load, said device having a first leakage capacitance between said output lead and said chassis ground and a second leakage capacitance between said return lead and chassis ground, means for sensing RF current leakage in said electrosurgical device comprising:

a first sensing capacitor is provided having first and second leads, said first lead of said first sensing capacitor being connected to said output lead of said generator, a second sensing capacitor is provided having a first and second connecting leads wherein said first lead of said second sensing capacitor is connected to said return lead of said generator, said second leads of said first and second capacitors being connected to each other, means for sensing an electrical imbalance between said first and second leakage capacitances and said first and second sensing capacitors which follow the relationship;

space="preserve" listing-type="equation">CL1/CS1=CL2/CS2

wherein;

CL1=said first leakage capacitance

CL2=said second leakage capacitance

CS1=said first sensing capacitor

CS2=said second sensing capacitor

means for reducing the output of said generator in response to said electrical imbalance between said first and second leakage capacitances and the first and second capacitors so that RF current leakage will be kept below a predetermined set value.